1. Field of the Invention
The present invention relates to a process of assembling an electromagnetic valve.
2. Description of the Related Art
An anti-lock brake system (ABS) is provided in a brake device of a vehicle in order to prevent locking of the wheels at times of sudden braking. Generally, an ABS is formed by a speed sensor, an ABS computer, an ABS actuator and the like. The ABS actuator includes a plurality of electromagnetic valves, pumps and the like.
An example of a conventional electromagnetic valve provided in an ABS actuator is illustrated in FIG. 6 (International Application Laid-Open No. WO92/05989). In this electromagnetic valve 60, a channel 64 is formed in a seat valve 62. A shaft 68 is provided with a valve element 66 which opens and closes the channel 64. The shaft 68 is supported by a guide 70 so as to be movable. Further, a plunger 72 is fixed to the shaft 68 at the opposite side of the valve element 66. A sleeve 74 is disposed at the periphery of the plunger 72. A core 76 is fixed to the sleeve 74 so as to oppose the plunger 72. The lower end portion of the sleeve 74 is caulked and fixed to a housing 78. A yoke 82 which accommodates a coil 80 is disposed at the periphery of the sleeve 74.
By energizing the coil 80, the plunger 72 is drawn against the urging force of a return spring 84 and moves together with the shaft 68. The valve element 66 moves away from the channel 64 so that the channel 64 is opened.
In the conventional electromagnetic valve 60 having the above-described structure, the respective parts are independently and successively assembled to the housing 78. Namely, the seat valve 62, the guide 70, the plunger 72 together with the shaft 68, and the like are successively assembled in a predetermined hole formed in the housing 78. After the sleeve 74, to which the core 76 is fixed, is made to cover the structure assembled as described above, a peripheral edge portion (caulking portion 86) of the hole is caulked so that the sleeve 74 is fixed to the housing 78. Thereafter, the yoke 82 (coil 80) is made to cover the sleeve 74. In this way, the electromagnetic valve 60 is completed.
However, in the conventional electromagnetic valve 60, because the respective structural parts are successively assembled to the housing 78 as described above, when the sleeve 74 is caulked and fixed to the housing 78, the sleeve 74 together with the core 76 is displaced with respect to the housing 78 due to the movement of the housing 78 which is caused by the caulking. A drawback arises in that it is difficult to determine the accurate attachment position off the sleeve 74. Accordingly, in this case, a gap .DELTA.G which is set appropriately during temporary assembly varies due to fixing the sleeve 74. This drawback becomes marked in cases in which the housing 78 is made of aluminum in order to make the electromagnetic valve 60 more lightweight.